Kozlov, V., Maz’ya, V. and Rossmann, J. 1998. Conic singularities of solutions to problems in hydrodynamics of a viscous fluid with a free surface. MATHEMATICA SCANDINAVICA. 83, 1 (Sep. 1998), 103–141. DOI:https://doi.org/10.7146/math.scand.a-13845.